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Why is superdeterminism not the universally accepted explanation of nonlocality? 
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#253
Mar412, 01:16 AM

PF Gold
P: 1,376

Otherwise yes, I do agree that this doesn't work. 


#254
Mar412, 09:51 AM

P: 1,583




#255
Mar412, 10:45 PM

Sci Advisor
PF Gold
P: 5,435

http://www.nature.com/nature/journal.../409791a0.html For reasons I do not fully understand, most local realists simply reject this by pointing out that the locality loophole (closed by Weihs et at in 1998) is not closed simultanoeously. 


#256
Mar412, 11:29 PM

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#257
Mar512, 03:49 AM

Sci Advisor
P: 4,627




#258
Mar512, 08:24 AM

P: 1,583

Also, what exactly is the Bohmian view of entanglement? 


#259
Mar512, 09:12 AM

Sci Advisor
P: 4,627




#260
Mar512, 10:02 AM

P: 1,583

Demystifer, if pilot waves don't go faster than light, then what explains the nonlocality of entanglement? Does the quantum potential propagate faster than light?
Also, am I wrong in my impression that a particle's trajectory right now is determined in part by the apparatuses it knows, based on nonlocal interaction, that it's going to encounter later? 


#261
Mar512, 11:48 AM

P: 1,414

The crux of why I think one can be a local determinist while still believing that Belltype LR models of quantum entanglement are ruled out is because of the assumption that what determines individual detection is not the same underlying parameter as what determines coincidental detection. The assumption regarding individual detection is that it's determined by the value of some locally produced (eg., via common emission source) property (eg., the electrical vector) of the photon incident on the polarizing filter. It's further assumed that this is varying randomly from entangled pair to entangled pair. So, there is a 50% reduction in detection rate at each of the individual detectors with the polarizers in place (compared to no polarizers), and a random accumulation of detections. (Wrt individual detection, LR and QM predictions are the same). The assumption regarding coincidental detection is that, wrt each entangled pair, what is being measured by the joint polarizer settings is the locally produced (eg., via common emission source) relationship between the polarizerincident photons of a pair. Because A and B always record identical results, (1,1) or (0,0) wrt a given coincidence interval when the polarizers are aligned, and because the rate of coincidental detection varies predictably (as cos^{2}θ in the ideal), then it's assumed that the underlying parameter (the locally produced relationship between the photons of a pair) determining coincidental detection isn't varying from pair to pair. It might be further assumed that the the value of the relevant property is the same for each photon of a given pair (ie., that the separated polarizers are measuring exactly the same value of the same property wrt any given pair). But that value only matters wrt individual detection, not wrt coincidental detection. And here's the problem. The LR program requires that coincidental detection be modeled in terms of the underlying parameter that determines individual detection. But how can it do that if the underlying parameter that determines coincidental detection is different than the underlying parameter that determines individual detection? There have been attempts to model entanglement this way (ie., in terms of an unchanging underlying parameter that doesn't vary from entangled pair to entangled pair), but they've rejected as being nonBelltype LR models. Regarding your 12 step LR reasoning (reproduced below), the problem begins in trying to understand coincidental detection in terms of step 2. I hope the above makes it clearer why I think that one can believe that the LR program (regarding the modelling of quantum entanglement) is kaput, while still believing that the best working assumptions are that our universe is evolving locally deterministically. And so, no need for superdeterministic theories of quantum entanglement.  


#262
Mar512, 12:27 PM

PF Gold
P: 1,376

Speaking about experiments, different experiments can have different loopholes or different sources of systematic errors. But photon tests are way ahead of other entanglement experiments in terms of attention they have got, analysis made and different modifications of similar experiments preformed. So I would like to stick to photon experiments. 


#263
Mar512, 05:31 PM

P: 57

If so, how could a coincidental parameter/function etc. possibly be different from an individual one? 


#264
Mar512, 05:58 PM

P: 1,414

The underlying parameter or function that determines coincidental detection is assumed to be the relationship between those values. This relationship is assumed to not vary from pair to pair, because the rate of coincidental detection varies, predictably, as a function of the angular difference between the joint polarizer settings. 


#265
Mar512, 06:05 PM

P: 1,583

ThomasT, I just don't understand your point. If you are a (nonsuperdeterministic) local determinist, and you find that entangled photons measured at polarizers oriented at the same angle behave identically, you can have only one possible response: "The photons are not coordinating their behavior through fasterthanlight communication. Rather they are each deciding to go through or not go the polarizer based on a common function P(θ), which equals 1 if the photon is supposed to go through and 0 if not." If you do not agree with this response, how can you consider yourself a local determinist?



#266
Mar512, 06:20 PM

P: 1,583




#267
Mar512, 06:30 PM

P: 1,414




#268
Mar512, 06:34 PM

P: 1,414




#269
Mar512, 06:49 PM

P: 57




#270
Mar512, 07:00 PM

P: 1,414

We're talking about different measurement parameters. Is it unreasonable to suppose that these different measurement parameters are measuring different underlying parameters? 


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